Adverse drug reactions in the liver are the most common reason for drugs to be taken off the market, and the federal Food and Drug Administration now wants better ways to detect these problem drugs before they reach the market and injure users. In an article published this week in the influential New England Journal of Medicine, lead author Victor J. Navarro, M.D., clinical associate professor of medicine at Jefferson Medical College of Thomas Jefferson University in Philadelphia, writes that liver injuries continue to plague the nation's drug development system, proving very costly to pharmaceutical companies that spend millions of dollars on development, only to find later that a new medicine is potentially toxic to the liver.